Process for separating potassium phosphate from potassium aluminate in solutions



Patented Aug. 23, 1932 UNITED STAH'IITES;

BUD OLF isms) SCHULZE, or BITTERFELD, GERMANY, ssrenoit j'ro iiarnn annrivnusrnriz AKTIENGESELLSCHAFT', or rennxron'r-onmnngnnm, qnmv nny E PROCESS FOR SEPARATING POTASSIUM PHOSPHATE m m: rorAssiui'vi ALUM nA'rni IN SOLUTIONS] if r No Drawing. Application filed November 15, 1930, Serial No. 496,037, and in Germany November 23, 1929 The present invention relates to an improved process for separating potassium phosphate from potassium aluminate in solutions.

When iron-alumina phosphates or raw materials containing said phosphates are treated with caustic potash lye, solutions are obtained, after separating the insoluble matter, which contain tri-potassium phosphate 10' and potassium aluminate together with an excess of caustic potash lye. Similar solutions are produced when mixtures of iron and alumina phosphates with potash, or with sulfate of potassium and carbon, or with chloride of potassium and carbon in the presence of steam, are subjected to roasting and subsequent leaching.

Although the main object of the present invention is the separate recovery of the trieo potassium phosphate and the potassium aluininate from such solutions, the process according to the present lnvention is by no means restricted to that purpose but is equally applicable to the separation of said compounds whenever simultaneously present in solutions.

I have observed that the treatment of solutions containing both tri-potassium phosphate and potassium aluminate with ammonia gas results in the formation of two separate liquid layers and that the lower layer contains the bulk of the phosphoric acid in form of a concentrated solution of tri-potassium phosphate together with a smaller quantity of aluminate, whereas the upper layer contains most of the aluminate. I have further found that when more diluted phosphate aluminate solutions are treated in this manner the percentage of the potassium 0 aluminate contained in the upper layer is increased at the expense of the quantity of that salt remaining in the lower layer. The potassium aluminate contained in the strongly ammoniacal upper layer is entirely stable as long as the solution still contains free alkali. In morefconcentrated solutions the distribution of the; aluminateis somewhat i shifted as an increasing amount of the alumi nate tends to pass into the lower layer. It. appears that the equilibrium of distribution of potassium aluminate is a functionof the:

"concentration of the solution: Withequal parts byweight of P 0 and A1 05 i-nthe original solution, the following 7 percentages of aluminate will be found to be present. in the upperammoniacal layer: f

Concentrationjot tri- Corilcentration of 1 potassium phosphate potasslum aluminate in the solution ,m'the upper! ayer I ,yPer cent Percent According, to the present, invention the. starting solution containing tri -potassium. phosphate andpotassium aluminatein suitable concentrationv is therefore treated with.

ammonia gasa'nd the upper liquidlayer tive solution isadjusted in suchan anner as to effect complete'separation with a minimumz'o f dilution, which of course will deterial. v The ammonia isjdriven off from the sepa rated solutions in the usual manner, forex ample, by evaporating, and is reused in the process.ffl.": a. The solution ofvtri-potassium phosphate pend on the compositionof the starting mav 7 may be worked up into potassium phosphates lovers HmP O; contents do notexceed about 7 up of the seharatedsolutions ield 83 kq's.

or into fertilizers, whereas the aluminate solution yields alumina and potash when subjected to a process known per se.

Example 100 kgs. of iron-alumina phosphate containing about 30 percent A1 0 8 percent -Fe O and 30 percent P 0 are heated with 1800 kgs. of a 7 percent caustic potash solution to 60 C. for 5 hours. Afterremoving theinsoluble matter, ammonia gaswis introduced at a temperature between 15 and 2( L I h up to saturation'r Two liquid layers are formed. which are separated from'ea'ch other.

'ture. p

liquid layers thusobtained into alumina, potash and potassium phosphate.

5. A process which comprises treating a S0ll1l3l01'1 containing tri-potassium phosphate I and potassium aluminate with ammonia gas so as to attain a substantial ammonia concentration in the solution, and separating the two liquid layers thereupon formed from each other.

In testimony-whereoLI ailix my slgna- RUDoLF SCHULZE.

Totb o e 1 v na ter d tio 5. 000;Q,v

lied until saturation is attained. The lower layer theni formed contains not morethan" about 1 or 2 percent of the alumina origin allv present. whereasin the combined upper 3 percent of the original quantity. Working tri-nota s m phosphate, 28 kgs. alumina, -64 kgs. potash.

I claim: 7

a solu tion containing 'tri-notassium phosphate and potassium 'aluminate with ammonia gas and separating the two liquid lay ers formed from each bther. f

2. A process which comprises saturating a solution containing tri-potassium phos phate and potassium 'aluminate' with ammonia gas. separatingthe two'liquid layers formed from each other. diluting the lower layer with a qi lantity of water, subjecting it a to another treatment with ammonia gas, and

recovering tri-pota'ssium phosphate from. the

kits. of water. ammonia gas is againsup- 1. 1A process which comprises saturating it combined respective lower liquid layers and V potassium aluminate from the" combined're- I so spective upper liquid layers;

3. A'process which comprisessaturating a I solution containing tri-potassium phosphate and potassium aluminate with ammonia gas, separating the two liquid layers formed from each'other, diluting the lower layer with a quantity of water, subjecting it to another treatment-wlth ammonia gas, and recovering v tri potassium phosphate from the combined respectivelower liquid layers and potassium aluminate from the combined respective upper liquid layers, the ammonia gas being V potash lye so as to obtain a solution'containing both tri-potassium phosphate and alumina phosphate, saturating said solution with ammoniafgas and workingup thetwo 

